The present invention is concerned primarily with a communication method providing duplex communication simultaneously between a plurality of pairs of stations on a single wire pair highway by frequency division multiplexing. Frequency division multiplexing to provide several channels on a single pair of wires is known for telephony. However, in telephone systems employed hitherto, the various carrier frequencies providing the frequency division multiplexed channels on the single wire pair are provided continuously irrespective of whether a particular channel is busy. This arrangement is quite satisfactory for large scale telephone installations where power consumption is of only minor concern. However, to provide frequency division multiplexing using known techniques for field telephone applications, operating from battery power supplies, would make excessive demands on the battery supplies enabling only relatively short life operation. Also, such an arrangement would reduce the flexibility of the field telephone system since the various stations on the field telephone "net" would have to operate through exchange apparatus which would provide channel routing and maintain the various frequency carrier signals.